Changeset 9752db in git

Timestamp:

May 10, 2012, 6:47:22 PM (11 years ago)

Author:

Martin Lee <martinlee84@…>

Branches:

(u'jengelh-datetime', 'ceac47cbc86fe4a15902392bdbb9bd2ae0ea02c6')(u'spielwiese', 'a800fe4b3e9d37a38c5a10cc0ae9dfa0c15a4ee6')

Children:

d0015c9c5906ccd1040927a2140a137a93d743b1

Parents:

5428647f3ac13d90ef45d257602f128804d6920a

git-author:

Martin Lee <martinlee84@web.de>2012-05-10 18:47:22+02:00

git-committer:

Oleksandr Motsak <motsak@mathematik.uni-kl.de>2012-05-15 18:37:46+02:00

Message:

chg: use irreducibility criterion also in characteristic 0

Location:

factory

Files:

• cfNewtonPolygon.cc (modified) (1 diff)
• cfNewtonPolygon.h (modified) (1 diff)
• facBivar.cc (modified) (1 diff)

factory/cfNewtonPolygon.cc

@@ -857 +857 @@
   return result;
 }
+
+bool irreducibilityTest (const CanonicalForm& F)
+{
+  int sizeOfNewtonPolygon;
+  int ** newtonPolyg= newtonPolygon (F, sizeOfNewtonPolygon);
+  if (sizeOfNewtonPolygon == 3)
+  {
+    bool check1=
+        (newtonPolyg[0][0]==0 || newtonPolyg[1][0]==0 || newtonPolyg[2][0]==0);
+    if (check1)
+    {
+      bool check2=
+        (newtonPolyg[0][1]==0 || newtonPolyg[1][1]==0 || newtonPolyg[2][0]==0);
+      if (check2)
+      {
+        bool isRat= isOn (SW_RATIONAL);
+        if (isRat)
+          Off (SW_RATIONAL);
+        CanonicalForm tmp= gcd (newtonPolyg[0][0],newtonPolyg[0][1]);
+        tmp= gcd (tmp, newtonPolyg[1][0]);
+        tmp= gcd (tmp, newtonPolyg[1][1]);
+        tmp= gcd (tmp, newtonPolyg[2][0]);
+        tmp= gcd (tmp, newtonPolyg[2][1]);
+        if (isRat)
+          On (SW_RATIONAL);
+        if (tmp == 1)
+        {
+          for (int i= 0; i < sizeOfNewtonPolygon; i++)
+            delete [] newtonPolyg [i];
+          delete [] newtonPolyg;
+        }
+        return (tmp==1);
+      }
+    }
+  }
+  for (int i= 0; i < sizeOfNewtonPolygon; i++)
+    delete [] newtonPolyg [i];
+  delete [] newtonPolyg;
+  return false;
+}

factory/cfNewtonPolygon.h

@@ -68 +68 @@
                   );
 
+/// computes the Newton polygon of F and checks if it satisfies the
+/// irreducibility criterion from S.Gao "Absolute irreducibility of polynomials
+/// via polytopes", Example 1
+///
+/// @return true if it satisfies the above criterion, false otherwise
+bool
+irreducibilityTest (const CanonicalForm& F ///<[in] a bivariate polynomial
+                   );
+
 #ifdef HAVE_NTL
 /// Algorithm 5 as described in Convex-Dense Bivariate Polynomial Factorization

factory/facBivar.cc

@@ -460 +460 @@
   }
 
+  if (irreducibilityTest (A))
+  {
+    CFList factors;
+    factors.append (A);
+
+    appendSwapDecompress (factors, conv (contentAxFactors),
+                          conv (contentAyFactors), false, false, N);
+
+    normalize (factors);
+    return factors;
+  }
   bool swap= false;
   if (degree (A) > degree (A, x))